In some cases we would want to refrain from cleaning up specific
openvswitch ports.
In Octavia, the health manager service is using a predefined[1]
openvswitch port which will gets nuked by the ovs_cleanup script in the
boot process.
That port is created by the operating system NIC configuration file
(by using OVS_EXTRA[2]), but due to the order of actions in the boot
process, the ovs_cleanup script gets invoked by systemd only at a later
stage. As a result the port will be deleted each time and the Octavia
health manager service will fail to bind.
This patch takes advantage of the 'external_ids' column that already
exists for ovs ports, in order to filter out ports we would like to
skip. We filter those ports by adding 'skip_cleanup' to the
'external_ids' column.
It is important to note that this will work if we append the following
to the port: -- set Interface o-hm0 external_ids:skip_cleanup=true"
Related-Bug: #1685223
[1] http://git.openstack.org/cgit/openstack/octavia/tree/devstack/plugin.sh?h=stable/ocata#n190
[2] https://github.com/osrg/openvswitch/blob/master/rhel/README.RHEL#L102
Change-Id: If483d0ee027596999370ab0d21b1743d4ef16acb
0a4596aa20